separate cbc proxy into separate clients

this is a pretty big and convoluted refactor unfortunately.

Previously:

There was one global `cbc_proxy_client` object in apps. This class has
the information about how to invoke the bt-ee lambda, and handles all
calls to lambda. This includes calls to the canary too (which is a
separate lambda).

The future:

There's one global `cbc_proxy_client`. This knows about the different
provider functions and lambdas, and you'll need to ask this client for a
proxy for your chosen provider. call cbc_proxy_client.get_proxy('ee')`
and it'll return you a proxy that knows what ee's lambda function is,
how to transform any content in a way that is exclusive to ee, and in
future how to parse any response from ee.

The present:

I also cleaned up some duplicate tests.
I'm really not sure about the names of some of these variables - in
particular `cbc_proxy_client` isn't a client - it's more of a java style
factory, where you call a function on it to get the client of your
choice.

tests/app/clients/test_cbc_proxy.py

@@ -1,13 +1,14 @@
 import json
 import uuid
+from unittest.mock import Mock
 
 import pytest
 
-from app.clients.cbc_proxy import CBCProxyClient, CBCProxyException
+from app.clients.cbc_proxy import CBCProxyClient, CBCProxyException, CBCProxyEE, CBCProxyCanary
 
 
 @pytest.fixture(scope='function')
-def cbc_proxy(client, mocker):
+def cbc_proxy_client(client, mocker):
     client = CBCProxyClient()
     current_app = mocker.Mock(config={
         'CBC_PROXY_AWS_ACCESS_KEY_ID': 'cbc-proxy-aws-access-key-id',
@@ -17,19 +18,39 @@ def cbc_proxy(client, mocker):
     return client
 
 
-def test_cbc_proxy_lambda_client_has_correct_region(cbc_proxy):
-    assert cbc_proxy._lambda_client._client_config.region_name == 'eu-west-2'
+@pytest.fixture
+def cbc_proxy_ee(cbc_proxy_client):
+    return cbc_proxy_client.get_proxy('ee')
 
 
-def test_cbc_proxy_lambda_client_has_correct_keys(cbc_proxy):
-    key = cbc_proxy._lambda_client._request_signer._credentials.access_key
-    secret = cbc_proxy._lambda_client._request_signer._credentials.secret_key
+@pytest.mark.parametrize('provider_name, expected_provider_class', [
+    ('ee', CBCProxyEE),
+    ('canary', CBCProxyCanary),
+])
+def test_cbc_proxy_client_returns_correct_client(provider_name, expected_provider_class):
+    mock_lambda = Mock()
+    cbc_proxy_client = CBCProxyClient()
+    cbc_proxy_client._lambda_client = mock_lambda
+
+    ret = cbc_proxy_client.get_proxy(provider_name)
+
+    assert type(ret) == expected_provider_class
+    assert ret._lambda_client == mock_lambda
+
+
+def test_cbc_proxy_lambda_client_has_correct_region(cbc_proxy_ee):
+    assert cbc_proxy_ee._lambda_client._client_config.region_name == 'eu-west-2'
+
+
+def test_cbc_proxy_lambda_client_has_correct_keys(cbc_proxy_ee):
+    key = cbc_proxy_ee._lambda_client._request_signer._credentials.access_key
+    secret = cbc_proxy_ee._lambda_client._request_signer._credentials.secret_key
 
     assert key == 'cbc-proxy-aws-access-key-id'
     assert secret == 'cbc-proxy-aws-secret-access-key'
 
 
-def test_cbc_proxy_create_and_send_invokes_function(mocker, cbc_proxy):
+def test_cbc_proxy_create_and_send_invokes_function(mocker, cbc_proxy_ee):
     identifier = 'my-identifier'
     headline = 'my-headline'
     description = 'my-description'
@@ -50,7 +71,7 @@ def test_cbc_proxy_create_and_send_invokes_function(mocker, cbc_proxy):
     }]
 
     ld_client_mock = mocker.patch.object(
-        cbc_proxy,
+        cbc_proxy_ee,
         '_lambda_client',
         create=True,
     )
@@ -59,7 +80,7 @@ def test_cbc_proxy_create_and_send_invokes_function(mocker, cbc_proxy):
         'StatusCode': 200,
     }
 
-    cbc_proxy.create_and_send_broadcast(
+    cbc_proxy_ee.create_and_send_broadcast(
         identifier=identifier,
         headline=headline,
         description=description,
@@ -86,7 +107,7 @@ def test_cbc_proxy_create_and_send_invokes_function(mocker, cbc_proxy):
     assert payload['expires'] == expires
 
 
-def test_cbc_proxy_create_and_send_handles_invoke_error(mocker, cbc_proxy):
+def test_cbc_proxy_create_and_send_handles_invoke_error(mocker, cbc_proxy_ee):
     identifier = 'my-identifier'
     headline = 'my-headline'
     description = 'my-description'
@@ -107,7 +128,7 @@ def test_cbc_proxy_create_and_send_handles_invoke_error(mocker, cbc_proxy):
     }]
 
     ld_client_mock = mocker.patch.object(
-        cbc_proxy,
+        cbc_proxy_ee,
         '_lambda_client',
         create=True,
     )
@@ -117,7 +138,7 @@ def test_cbc_proxy_create_and_send_handles_invoke_error(mocker, cbc_proxy):
     }
 
     with pytest.raises(CBCProxyException) as e:
-        cbc_proxy.create_and_send_broadcast(
+        cbc_proxy_ee.create_and_send_broadcast(
             identifier=identifier,
             headline=headline,
             description=description,
@@ -134,7 +155,7 @@ def test_cbc_proxy_create_and_send_handles_invoke_error(mocker, cbc_proxy):
     )
 
 
-def test_cbc_proxy_create_and_send_handles_function_error(mocker, cbc_proxy):
+def test_cbc_proxy_create_and_send_handles_function_error(mocker, cbc_proxy_ee):
     identifier = 'my-identifier'
     headline = 'my-headline'
     description = 'my-description'
@@ -155,7 +176,7 @@ def test_cbc_proxy_create_and_send_handles_function_error(mocker, cbc_proxy):
     }]
 
     ld_client_mock = mocker.patch.object(
-        cbc_proxy,
+        cbc_proxy_ee,
         '_lambda_client',
         create=True,
     )
@@ -166,7 +187,7 @@ def test_cbc_proxy_create_and_send_handles_function_error(mocker, cbc_proxy):
     }
 
     with pytest.raises(CBCProxyException) as e:
-        cbc_proxy.create_and_send_broadcast(
+        cbc_proxy_ee.create_and_send_broadcast(
             identifier=identifier,
             headline=headline,
             description=description,
@@ -183,11 +204,13 @@ def test_cbc_proxy_create_and_send_handles_function_error(mocker, cbc_proxy):
     )
 
 
-def test_cbc_proxy_send_canary_invokes_function(mocker, cbc_proxy):
+def test_cbc_proxy_send_canary_invokes_function(mocker, cbc_proxy_client):
     identifier = str(uuid.uuid4())
 
+    canary_client = cbc_proxy_client.get_proxy('canary')
+
     ld_client_mock = mocker.patch.object(
-        cbc_proxy,
+        canary_client,
         '_lambda_client',
         create=True,
     )
@@ -196,7 +219,7 @@ def test_cbc_proxy_send_canary_invokes_function(mocker, cbc_proxy):
         'StatusCode': 200,
     }
 
-    cbc_proxy.send_canary(
+    canary_client.send_canary(
         identifier=identifier,
     )
 
@@ -213,66 +236,11 @@ def test_cbc_proxy_send_canary_invokes_function(mocker, cbc_proxy):
     assert payload['identifier'] == identifier
 
 
-def test_cbc_proxy_send_canary_handles_invoke_error(mocker, cbc_proxy):
+def test_cbc_proxy_send_link_test_invokes_function(mocker, cbc_proxy_ee):
     identifier = str(uuid.uuid4())
 
     ld_client_mock = mocker.patch.object(
-        cbc_proxy,
-        '_lambda_client',
-        create=True,
-    )
-
-    ld_client_mock.invoke.return_value = {
-        'StatusCode': 400,
-    }
-
-    with pytest.raises(CBCProxyException) as e:
-        cbc_proxy.send_canary(
-            identifier=identifier,
-        )
-
-    assert e.match('Could not invoke lambda')
-
-    ld_client_mock.invoke.assert_called_once_with(
-        FunctionName='canary',
-        InvocationType='RequestResponse',
-        Payload=mocker.ANY,
-    )
-
-
-def test_cbc_proxy_send_canary_handles_function_error(mocker, cbc_proxy):
-    identifier = str(uuid.uuid4())
-
-    ld_client_mock = mocker.patch.object(
-        cbc_proxy,
-        '_lambda_client',
-        create=True,
-    )
-
-    ld_client_mock.invoke.return_value = {
-        'StatusCode': 200,
-        'FunctionError': 'something',
-    }
-
-    with pytest.raises(CBCProxyException) as e:
-        cbc_proxy.send_canary(
-            identifier=identifier,
-        )
-
-    assert e.match('Function exited with unhandled exception')
-
-    ld_client_mock.invoke.assert_called_once_with(
-        FunctionName='canary',
-        InvocationType='RequestResponse',
-        Payload=mocker.ANY,
-    )
-
-
-def test_cbc_proxy_send_link_test_invokes_function(mocker, cbc_proxy):
-    identifier = str(uuid.uuid4())
-
-    ld_client_mock = mocker.patch.object(
-        cbc_proxy,
+        cbc_proxy_ee,
         '_lambda_client',
         create=True,
     )
@@ -281,7 +249,7 @@ def test_cbc_proxy_send_link_test_invokes_function(mocker, cbc_proxy):
         'StatusCode': 200,
     }
 
-    cbc_proxy.send_link_test(
+    cbc_proxy_ee.send_link_test(
         identifier=identifier,
     )
 
@@ -297,58 +265,3 @@ def test_cbc_proxy_send_link_test_invokes_function(mocker, cbc_proxy):
 
     assert payload['identifier'] == identifier
     assert payload['message_type'] == 'test'
-
-
-def test_cbc_proxy_send_link_test_handles_invoke_error(mocker, cbc_proxy):
-    identifier = str(uuid.uuid4())
-
-    ld_client_mock = mocker.patch.object(
-        cbc_proxy,
-        '_lambda_client',
-        create=True,
-    )
-
-    ld_client_mock.invoke.return_value = {
-        'StatusCode': 400,
-    }
-
-    with pytest.raises(CBCProxyException) as e:
-        cbc_proxy.send_link_test(
-            identifier=identifier,
-        )
-
-    assert e.match('Could not invoke lambda')
-
-    ld_client_mock.invoke.assert_called_once_with(
-        FunctionName='bt-ee-1-proxy',
-        InvocationType='RequestResponse',
-        Payload=mocker.ANY,
-    )
-
-
-def test_cbc_proxy_send_link_test_handles_function_error(mocker, cbc_proxy):
-    identifier = str(uuid.uuid4())
-
-    ld_client_mock = mocker.patch.object(
-        cbc_proxy,
-        '_lambda_client',
-        create=True,
-    )
-
-    ld_client_mock.invoke.return_value = {
-        'StatusCode': 200,
-        'FunctionError': 'something',
-    }
-
-    with pytest.raises(CBCProxyException) as e:
-        cbc_proxy.send_link_test(
-            identifier=identifier,
-        )
-
-    assert e.match('Function exited with unhandled exception')
-
-    ld_client_mock.invoke.assert_called_once_with(
-        FunctionName='bt-ee-1-proxy',
-        InvocationType='RequestResponse',
-        Payload=mocker.ANY,
-    )